Vacuum packaging involves removing air or other gases from a storage container and then sealing the container to prevent the contents from being exposed to the air. Vacuum packaging is particularly useful in protecting food and other perishables against oxidation. Oxygen is a main cause of food spoilage and contributes to the growth of bacteria, mold, and yeast. Accordingly, vacuum packaged food often lasts three to five times longer than food stored in ordinary containers. Moreover, vacuum packaging is useful for storing clothes, photographs, silver, and other items to prevent discoloration, corrosion, rust, and tarnishing. Furthermore, vacuum packaging produces tight, strong, and compact packages to reduce the bulk of articles and allow for more space to store other supplies.
FIGS. 1A and 1B are schematic isometric views of a conventional appliance 80 for vacuum packaging an object 79 in accordance with the prior art. The vacuum packaging appliance 80 includes a base 82, a hood 90 pivotably coupled to the base 82, a lower trough 84, an upper trough (not shown) aligned with the lower trough 84, and a vacuum pump (not shown) operably coupled to the upper trough. The hood 90 pivots between an open position (shown in FIG. 1B) in which a bag 70 can be placed between the hood 90 and the base 82 and a closed position (shown in FIG. 1A) in which the bag 70 can be evacuated and thermally sealed.
In the closed position of FIG. 1A, the upper trough and the lower trough 84 form a vacuum chamber to remove gas from the interior of the bag 70. The base 82 also includes a seal 85 surrounding the vacuum chamber to seal the chamber from ambient air while gas is removed from the interior of the bag 70. The vacuum packaging appliance 80 also includes a heating element 88 to thermally seal the bag 70 after the gas has been evacuated.
Conventional vacuum packaging bags include two panels attached together with an open end. Typically, the panels each include two or more layers. The inner layer can be a heat sealable material, and the outer layer can be a gas impermeable material to provide a barrier against the influx of air. The plasticity temperature of the inner layer is lower than the outer layer. Accordingly, the bag can be heated to thermally bond the inner layer of each panel together to seal the bag without melting or puncturing the outer layer during the heat sealing cycle.
A conventional vacuum packaging process includes depositing the object 79 into the bag 70 and positioning an open end 71 of the bag 70 proximate to the lower trough 84 of the vacuum packaging appliance 80. Next, the hood 90 pivots downward to form the vacuum chamber around the open end 71 of the bag 70. The vacuum pump then removes gas from the vacuum chamber and the interior of the bag 70, which is in fluid communication with the vacuum chamber. After the gas has been removed from the interior of the bag 70, the heating element 88 heats a strip of the bag 70 proximate to the open end 71 to melt the inner layer of each panel and thermally seal the bag 70.
FIG. 2 is a flow chart illustrating a method 10 for operation of the vacuum pump of the vacuum packaging appliance in accordance with a conventional vacuum packaging process. A step 12 involves coupling a storage receptacle to a vacuum circuit of the vacuum packaging appliance. As will be appreciated, the vacuum circuit is coupled to the vacuum pump such that actuation of the vacuum pump results in evacuation of the vacuum circuit. By coupling the storage receptacle (bag as described above, canister, etc.) to the vacuum circuit, actuation of the vacuum pump will result in evacuation of the storage receptacle.
A step 14 hermetically closes the vacuum circuit. For example, step 14 may correspond to closing the hood 90 as described above. Step 14 insures that evacuation of the storage receptacle will result eventually in the storage receptacle reaching a gas pressure that is sufficiently near absolute vacuum to accomplish the intended purpose.
A step 16 actuates the vacuum pump at a constant evacuation speed fixed by the control circuitry of the vacuum packaging appliance. Step 16 is accomplished manually by a user actuating a control switch. This control switch may be attached to a button made available to the user, or may be formed into the vacuum packaging appliance such that when the vacuum circuit is hermetically sealed, the control switch actuates. The vacuum pump operates at the constant predefined evacuation speed until the user turns the machine off, or in some instances a vacuum sensor is placed in the vacuum circuit and the vacuum pump is turned off when the vacuum of the vacuum circuit reaches a certain predefined level.
FIG. 3 is a graphical illustration 50 symbolic of a vacuum level 52 of a bag-like storage receptacle (“bag”) during evacuation via the prior art single speed evacuation. As can be seen, the bag maintains a substantially constant vacuum level during an initial phase 54 of evacuation. The substantially constant vacuum level of the initial phase 54 results from the volume of the bag adjusting substantially proportionally to the volume of gas evacuated from the bag. Once the volume of the bag has compressed to a critical volume (depends upon the bag etc.), evacuation of the bag begins to substantially decrease bag pressure as shown during the critical phase 56 of vacuum level 52. Assuming the pump is allowed to continuously operate, the vacuum level 52 of the bag will reach a final level during a final phase 58. The final vacuum level will be determined by the strength of the vacuum pump.
The prior art teaches a single, constant speed vacuum pump. During the initial phase, the vacuum pump is not taxed, however during the critical phase and the final phase, the vacuum pump can be taxed. The vacuum speed of the prior art must be selected such that the pump motor operates safely during all phases of evacuation. A desirable feature to most users of the vacuum packaging appliance is to evacuate the bag as fast as possible. Thus the prior art teaches setting the vacuum pump evacuation speed as fast as will safely operate during the critical and final phases.
Unfortunately, this single, high-speed approach is not well suited for fragile contents in collapsible bags, as the user cannot stop the vacuum in time. Additionally, there are periods of evacuation when the vacuum pump could be run at higher rates without causing damage to the vacuum pump. This means the prior art teaching does not optimize evacuation speed.
Another problem with conventional vacuum packaging appliances is the lack of vacuum level feedback information provided to the user. During evacuation the user has no knowledge of the vacuum level at any given point in time. As a result, the user has to make a visual determination when to turn off the machine or rely on the machine's predefined vacuum level to automatically stop the vacuum pump. A lack of user interaction may result in damaging fragile contents and in some instances, may result in incomplete evacuation due to the storage receptacle.
The capability to sense various vacuum levels with user feedback would be particularly useful when the content in a collapsible storage receptacle is fragile. For example, when storing fragile items a user may want to deactivate the vacuum pump during the critical phase to avoid damaging the fragile contents. In other circumstances, the user may choose to prolong evacuation until the vacuum level reaches the final phase 58 to prevent incomplete evacuation. This functionality is not accomplished by the prior art.
Accordingly, there is a need for user feedback information regarding vacuum levels during evacuation to facilitate user interaction with the vacuum packaging appliance. Additionally, there is a need for more sophisticated vacuum sensing and vacuum pump control.